1. Field of Invention
The invention concerns a process for the conversion of carbon dioxide by a reaction thereof with epoxide (olefin oxide) and a subsequent conversion to alkylenecarbonate. For the first time, tert-butyl-substituted mono- and diphthalocyanine complexes of metals are provided as catalysts for this process.
2. Related Art
The development of a process for conversion of carbon dioxide, the concentration of which, in the atmosphere, is increasing gradually, is urgently sought. A promising approach for removing carbon dioxide from its circulation is conversion thereof into ecologically safe polymers (for example, polypropylenecarbonates). Therefore the search for processes to synthesize initial monomer substances (in particular alkylenecarbonates) from carbon dioxide, for the purpose of subsequent converting the monomers into polymers, represents a rather urgent problem.
The reactions between alkylene oxides and carbon dioxide in the presence of catalysts are known: see U.S. Pat. Nos. 2,773,070; 2,873,282; 3,535,341; 4,786,741; European Patent No. 0 297 647; and Japanese Patent Publication No. 63-181765. As a rule, catalysts used in these reactions were halogen-containing compounds at a rather large concentration, the application of which results in formation of a large quantity of impurities. In addition, most catalysts previously proposed lose activity in the given reactions, or rather promote interaction between epoxide molecules, instead of with carbon dioxide. Therefore there is the requirement for catalysts which are not destroyed during the conversion of carbon dioxide, do not add impurities to products of reaction and allow effective assimilation of carbon dioxide resulting in a reduction in the environment.
The process closest to the present invention is a process for formating alkylenecarbonates using phthalocyanine complexes of metals as catalysts, described in the U.S. Pat. No. 5,283,356. A drawback of this method is the low solubility of the used catalysts, that results, apparently, in a heterogeneous progression of the process with very low efficiency. In addition, a reaction in heterogeneous conditions does not allow to reach quantitative conversion of carbon dioxide, and, accordingly, much reduces the efficiency of said process.